Mach Tuck

Mach Tuck is an aerodynamic phenomenon where an aircraft experiences a nose-down pitching moment as it approaches the critical Mach number (transonic speed). As shock waves form on the wing, the center of lift shifts rearward, creating an increasing nose-down tendency.

If uncorrected, Mach tuck can lead to an uncontrollable dive. Modern airliners have Mach trim systems that automatically compensate for this tendency, and the flight envelope protection prevents the aircraft from reaching speeds where Mach tuck becomes dangerous.